Field effect transistor with stacked nanowire-like channels and methods of manufacturing the same

ABSTRACT

A CMOS circuit includes a partial GAA nFET and a partial GAA pFET. The nFET and the pFET each include a fin including a stack of nanowire-like channel regions and a dielectric separation region extending completely between first and second nanowire-like channel regions of the stack. The nFET and the pFET each also include a source electrode and a drain electrode on opposite sides of the fin, and a gate stack extending along a pair of sidewalls of the stack of nanowire-like channel regions. The gate stack includes a gate dielectric layer and a metal layer on the gate dielectric layer. The metal layer does not extend between the first and second nanowire-like channel regions. The channel heights of the nanowire-like channel regions of the partial GAA nFET and the partial GAA pFET are different.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Application No. 62/559,207, filed Sep. 15, 2017, and is acontinuation-in-part of U.S. patent application Ser. No. 15/458,655,filed Mar. 14, 2017, which claims priority to and the benefit of U.S.Provisional Patent Application No. 62/412,179, entitled “Partial GAANanowire-like FET with Stacked Nanowire-Like Channels with SimpleManufacturing Flow,” filed Oct. 24, 2016 in the U.S. Patent andTrademark Office, the entire contents of each of which are incorporatedherein by reference.

FIELD

The present disclosure relates generally to field effect transistors andmethods of manufacturing field effect transistors.

BACKGROUND

Conventional circuits are commonly formed from non-planar “fin” fieldeffect transistors (finFETs). Conventional finFETs generally includemultiple vertical fins serving as conducting channel regions. Narrowingthe width of the fin channel regions improves gate control of thepotential in the fin channel regions. Accordingly, conventional finFETsmay be provided with narrow fin widths to reduce short-channel effectsand thus enable scaling to shorter gate lengths. However, as gatelengths are scaled, conventional finFETs may fail to provide the desiredperformance (e.g., I_(eff)-I_(off)). Additionally, conventional finFETsare not a gate-all-around (GAA) structure, and therefore gate control isonly on sides of the fins, which limits further gate length scaling.

Future technologies have contemplated forming circuits from eithergate-all-around (GAA) nanowire (NW) FETs or GAA nanosheet (NS) FETs inorder to reduce short-channel effects and thereby enable scaling toshorter gate lengths. However, both GAA NW FETs and GAA NS FETs presentintegration problems. For instance, GAA FETs require an internal spacerto separate the GAA gate metal from the source/drain regions to reduceparasitic capacitance. Additionally, GAA FETs generally require that theGAA gate metal is formed in a narrow vertical region between the bottomof an overlying channel region and the top of an underlying channelregion to reduce parasitic capacitance. However, forming the GAA gatemetal in a narrow vertical region between the channel regions makes itdifficult to achieve the desired threshold voltage (V_(t)).

SUMMARY

The present disclosure is directed to various embodiments of a CMOScircuit. In one embodiment, the CMOS circuit includes a partial GAA nFETand a partial GAA pFET. The partial GAA nFET and the partial GAA pFETeach include a fin including a stack of nanowire-like channel regions.The stack includes at least a first nanowire-like channel region and asecond nanowire-like channel region stacked on the first nanowire-likechannel region. The partial GAA nFET and the partial GAA pFET each alsoinclude a dielectric separation region between the first and secondnanowire-like channel regions. The dielectric separation region extendscompletely from a surface of the second nanowire-like channel regionfacing the first nanowire-like channel region to a surface of the firstnanowire-like channel region facing the second nanowire-like channelregion. The partial GAA nFET and the partial GAA pFET each also includea source electrode and a drain electrode on opposite sides of the fin.The CMOS circuit also includes a gate stack extending along a pair ofsidewalls of the stack of nanowire-like channel regions for each of thepartial GAA nFET and the partial GAA pFET. The gate stack includes agate dielectric layer and a metal layer on the gate dielectric layer.The metal layer of the gate stack does not extend between the first andsecond nanowire-like channel regions. An nFET channel height of each ofthe first and second nanowire-like channel regions of the partial GAAnFET is different than a pFET channel height of each of the first andsecond nanowire-like channel regions of the partial GAA pFET.

The nFET channel height may be less than the pFET channel height. ThenFET channel height may be from approximately 2 nm to approximately 6nm, and the pFET channel height may be from approximately 4 nm toapproximately 6 nm. The nFET channel height may be from approximately 3nm to approximately 4 nm, and the pFET channel height may be fromapproximately 4 nm to approximately 5 nm.

A height of the dielectric separation region of the partial GAA nFET maydifferent than a height of the dielectric separation region of thepartial GAA pFET. The height of the dielectric separation region of thepartial GAA nFET may be greater than the height of the dielectricseparation region of the pFET.

A first sum of the nFET channel height and a height of the dielectricseparation region of the partial GAA nFET may be substantially equal toa second sum of the pFET channel height and a height of the dielectricseparation region of the partial GAA pFET. The first and second sums mayeach be from approximately 5 nm to approximately 12 nm.

The dielectric separation regions of the partial GAA nFET and thepartial GAA pFET may each include a portion of the gate dielectric layerof the gate stack. A dielectric material of the dielectric separationregion of the partial GAA nFET and the partial GAA pFET may be differentthan a dielectric material of the gate dielectric layer of the partialGAA nFET and the partial GAA pFET.

The gate dielectric layer may have a thickness from approximately 1 nmto approximately 3 nm.

The first and second nanowire-like channel regions of the partial GAAnFET or the partial GAA pFET may each have a width from approximately 3nm to approximately 8 nm.

The present disclosure is also directed to various embodiments of amethod of forming a CMOS circuit including a partial GAA nFET and apartial GAA pFET. In one embodiment, the method includes forming a stackof alternating sacrificial layers and conducting channel layers on asubstrate and etching the stack to form a first fin of the partial GAAnFET and a second fin of the partial GAA pFET. Each of the first andsecond fins includes a stack of nanowire-like channel regions, and thestack includes at least a first nanowire-like channel region and asecond nanowire-like channel region stacked on the first nanowire-likechannel region. The method also includes forming source and drainelectrodes for the partial GAA nFET and forming source and drainelectrodes for the partial GAA pFET. The method further includes maskingthe second fin of the partial GAA pFET and removing a portion of thestack of nanowire-like channel regions of the first fin such that aheight of each of the first and second nanowire-like channel regions ofthe first fin is less than a height of each of the first and secondnanowire-like channel regions of the second fin. The method alsoincludes forming, for each of the first and second fins, a dielectricseparation region between the first and second nanowire-like channelregions of the stack of nanowire-like channel regions. The dielectricseparation region extends completely from a surface of the secondnanowire-like channel region facing the first nanowire-like channelregion to a surface of the first nanowire-like channel region facing thesecond nanowire-like channel region. The method also includes forming agate stack including a gate dielectric layer and a metal layer on thegate dielectric layer. The gate stack extends along a pair of sidewallsof the stack of nanowire-like channel regions for each of the first andsecond fins. For each of the first and second fins, the metal layer ofthe gate stack does not extend between the first and secondnanowire-like channel regions of the stack of nanowire-like channelregions.

Removing the portion of the stack of nanowire-like channel regions ofthe first fin may be performed by a strip process, a cleaning process,an ashing process, an etching process, an oxidation process, orcombinations thereof.

The dielectric separation region of the first fin or the second fin maybe formed during the forming of the gate stack, and the dielectricseparation region of the first fin or the second fin may include aportion of the gate dielectric layer of the gate stack. The dielectricseparation region of each of the first and second fins may be formedbefore the forming of the gate stack, and a material of the dielectricseparation region of each of the first and second fins may be differentthan a material of the gate dielectric layer.

Forming the source and drain electrodes of the partial GAA pFET mayinclude depositing an Si buffer layer followed by depositing a layer ofSiGe or SiGeB. Forming the source and drain electrodes of the partialGAA nFET may include depositing an Si layer.

The conducting channel layers may include Si, the sacrificial layers mayinclude SiGe, and the Ge content of the SiGe may be from approximately10% to approximately 50%.

The method may also include removing a portion of the stack ofnanowire-like channel regions of the second fin. The portion of thestack of nanowire-like channel regions of the first fin that is removedmay be greater than the portion of the stack of nanowire-like channelregions of the second fin that is removed.

This summary is provided to introduce a selection of features andconcepts of embodiments of the present disclosure that are furtherdescribed below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used in limiting the scope of theclaimed subject matter. One or more of the described features may becombined with one or more other described features to provide a workabledevice.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of embodiments of the presentdisclosure will become more apparent by reference to the followingdetailed description when considered in conjunction with the followingdrawings. In the drawings, like reference numerals are used throughoutthe figures to reference like features and components. The figures arenot necessarily drawn to scale.

FIGS. 1A-1B are a schematic perspective view and a schematiccross-sectional view, respectively, of a field effect transistor (FET)according to one embodiment of the present disclosure; and

FIGS. 2A-2B depict a schematic cross-sectional view and a schematic topview, respectively, of a task of a method of forming a FET according toone embodiment of the present disclosure;

FIGS. 2C-2D depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the FETaccording to one embodiment of the present disclosure;

FIG. 2E depicts a schematic top view of a further task of the method offorming the FET according to one embodiment of the present disclosure;

FIGS. 2F-2G depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the FETaccording to one embodiment of the present disclosure;

FIGS. 2H-2I depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the FETaccording to one embodiment of the present disclosure;

FIGS. 2J-2K depict a schematic cross-sectional view and a schematic topview, respectively, of a further task of the method of forming the FETaccording to one embodiment of the present disclosure;

FIGS. 3A-3B are a schematic perspective view and a schematiccross-sectional view, respectively, of a CMOS circuit according to oneembodiment of the present disclosure;

FIGS. 4A-4B depict a schematic cross-sectional view and a schematic topview, respectively, of a task of a method of forming a CMOS circuitaccording to one embodiment of the present disclosure;

FIGS. 4C-4D depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the CMOScircuit according to one embodiment of the present disclosure;

FIG. 4E depicts a schematic top view of a further task of the method offorming the CMOS circuit according to one embodiment of the presentdisclosure;

FIGS. 4F-4G depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the CMOScircuit according to one embodiment of the present disclosure;

FIG. 4H depicts a schematic cross-sectional view of a further task ofthe method of forming the CMOS circuit according to one embodiment ofthe present disclosure;

FIGS. 4I-4J depict a schematic cross-sectional view and a schematic topview, respectively, of another task of the method of forming the CMOScircuit according to one embodiment of the present disclosure;

FIGS. 4K-4L depict a schematic cross-sectional view and a schematic topview, respectively, of a further task of the method of forming the CMOScircuit according to one embodiment of the present disclosure;

FIG. 5 is a graph depicting the saturated drain current (Idsat) of annFET of a CMOS circuit according to one embodiment of the presentdisclosure as a function of channel height; and

FIG. 6 is a graph depicting the saturated drain current (Idsat) of apFET of a CMOS circuit according to one embodiment of the presentdisclosure as a function of channel height.

DETAILED DESCRIPTION

The present disclosure is directed to various embodiments of a fieldeffect transistor (FET) and methods of manufacturing the same. The FETsof the present disclosure include a stack of nanowire-like channels anda gate stack including a dielectric layer and a metal layer. Accordingto one or more embodiments of the present disclosure, the dielectriclayer of the gate stack extends completely around each of thenanowire-like channels, whereas the metal layer of the gate stackextends along sides of the nanowire-like channels, but does not extendbetween adjacent nanowire-like channels in the stack of nanowire-likechannels. Accordingly, the FETs of the present disclosure arepartial-GAA nanowire-like FETs (i.e., partial GAA NW-like FETs).Providing the full gate stack (i.e., the dielectric layer and the metallayer) along the sides of the nanowire-like channels affords improvedcontrol of the channel potential compared to conventional finFETs due togate coupling to each nanowire-like channel through the dielectric layerat the top and bottom of each nanowire-like channel in addition to thegate coupling to each nanowire-like channel through the dielectric layeralong the sides of each nanowire-like channel. The FETs of the presentdisclosure are configured to enable scaling to shorter gate lengthscompared to conventional FETs by improving gate control of the potentialin the conducting fin channel regions. The FETs of the presentdisclosure are also configured to enable these shorter gate lengthswithout creating the integration problems associated with conventionalfull gate-all-around (GAA) nanosheet FETs and full GAA nanowire FETs.

Hereinafter, example embodiments will be described in more detail withreference to the accompanying drawings, in which like reference numbersrefer to like elements throughout. The present invention, however, maybe embodied in various different forms, and should not be construed asbeing limited to only the illustrated embodiments herein. Rather, theseembodiments are provided as examples so that this disclosure will bethorough and complete, and will fully convey the aspects and features ofthe present invention to those skilled in the art. Accordingly,processes, elements, and techniques that are not necessary to thosehaving ordinary skill in the art for a complete understanding of theaspects and features of the present invention may not be described.Unless otherwise noted, like reference numerals denote like elementsthroughout the attached drawings and the written description, and thus,descriptions thereof may not be repeated.

In the drawings, the relative sizes of elements, layers, and regions maybe exaggerated and/or simplified for clarity. Spatially relative terms,such as “beneath,” “below,” “lower,” “under,” “above,” “upper,” and thelike, may be used herein for ease of explanation to describe one elementor feature's relationship to another element(s) or feature(s) asillustrated in the figures. It will be understood that the spatiallyrelative terms are intended to encompass different orientations of thedevice in use or in operation, in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” or “under” otherelements or features would then be oriented “above” the other elementsor features. Thus, the example terms “below” and “under” can encompassboth an orientation of above and below. The device may be otherwiseoriented (e.g., rotated 90 degrees or at other orientations) and thespatially relative descriptors used herein should be interpretedaccordingly.

It will be understood that, although the terms “first,” “second,”“third,” etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a first element, component, region, layer or sectiondescribed below could be termed a second element, component, region,layer or section, without departing from the spirit and scope of thepresent invention.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to,” or “coupled to” another element or layer, itcan be directly on, connected to, or coupled to the other element orlayer, or one or more intervening elements or layers may be present. Inaddition, it will also be understood that when an element or layer isreferred to as being “between” two elements or layers, it can be theonly element or layer between the two elements or layers, or one or moreintervening elements or layers may also be present.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the present invention.As used herein, the singular forms “a” and “an” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and “including,” when used in thisspecification, specify the presence of the stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

As used herein, the term “substantially,” “about,” and similar terms areused as terms of approximation and not as terms of degree, and areintended to account for the inherent variations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. Further, the use of “may” when describing embodiments of thepresent invention refers to “one or more embodiments of the presentinvention.” As used herein, the terms “use,” “using,” and “used” may beconsidered synonymous with the terms “utilize,” “utilizing,” and“utilized,” respectively. Also, the term “exemplary” is intended torefer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present specification, and should not be interpreted in an idealizedor overly formal sense, unless expressly so defined herein.

With reference now to FIGS. 1A-1B, a field effect transistor (FET) 100according to one embodiment of the present disclosure includes a sourceelectrode 101, a drain electrode 102, at least one fin 103 extendingbetween the source and drain electrodes 101, 102, and a gate stack 104including a gate dielectric layer 105 and a metal layer 106 on thedielectric layer 105. The source and drain electrodes 101, 102, the fin103, and the gate stack 104 are formed on a substrate 107 (e.g., abulk-silicon substrate or a silicon-on-insulator (SOI) substrate). Asillustrated in FIG. 1B, each of the fins 103 is divided or separatedinto a stack of discrete nanowire-like channel regions 108. Although inthe illustrated embodiment the stack includes three nanowire-likechannel regions 108, in one or more embodiments, the stack may includeany other suitable number of nanowire-like channel regions 108, such astwo channel regions or more than three channel regions. In one or moreembodiments, the nanowire-like channel regions 108 may be strained.

As illustrated in FIG. 1B, the gate dielectric layer 105, or a portionof the gate dielectric layer 105, of the gate stack 104 extendscompletely around each of the nanowire-like channel regions 108 (i.e.,the gate dielectric layer 105, or a portion of the gate dielectric layer105, of the gate stack 104 extends along an upper surface 109, a lowersurface 110, and a pair of opposing sidewalls or side surfaces 111, 112of each of the nanowire-like channel regions 108). Accordingly, in theillustrated embodiment, for each pair of adjacent nanowire-like channelregions 108, the gate dielectric layer 105 or a portion of the gatedielectric layer 105 of the gate stack 104 separates the upper surface109 of the underlying nanowire-like channel region 108 from the lowersurface 110 of the overlying nanowire-like channel region 108.Additionally, in the illustrated embodiment, the metal layer 106 of thegate stack 104 extends along the side surfaces 111, 112 of thenanowire-like channel regions 108 and along the upper surface 109 of theuppermost nanowire-like channel region 108 (i.e., the metal layer 106extends around or covers the nanowire-like channel regions 108 of thefin 103) but the metal layer 106 does not extend between adjacentnanowire-like channel regions 108 or between the lowermost nanowire-likechannel region 108 and the substrate 107. Accordingly, in theillustrated embodiment, the full gate stack 104 (i.e., the gatedielectric layer 105 and the metal layer 106) does not extend fully orcompletely around each of the nanowire-like channel regions 108 suchthat the FET 100 of the present disclosure is a partial gate-all-around(GAA) FET rather than a full GAA FET. Providing the full gate stack 104along the side surfaces 111, 112 of the nanowire-like channels 108affords improved control of the channel potential compared to aconventional finFET structure due to gate coupling to each nanowire-likechannel region 108 through the gate dielectric layer 105 along the upperand lower surfaces 109, 110 of each nanowire-like channel 108 inaddition to the gate coupling to each nanowire-like channel region 108through the gate dielectric layer 105 along the side surfaces 111, 112of each of the nanowire-like channel regions 108.

In one or more embodiments, the gate dielectric layer 105 of the gatestack 104 may not extend, or may not substantially extend, betweenadjacent nanowire-like channel regions 108 and the FET 100 may include aseparate dielectric layer vertically separating adjacent nanowire-likechannel regions 108. The separate dielectric layer may be formed from adielectric material different than a dielectric material of the gatedielectric layer 105 of the gate stack 104. That is, the dielectriclayer may extend along the upper and lower surfaces 109, 110 of thenanowire-like channel regions 108 and the gate dielectric layer 105 mayextend along the side surfaces 111, 112 of the nanowire-like channelregions 108 such that the dielectric constant of the dielectric layerextending between adjacent nanowire-like channel regions 108 (e.g.,along upper and lower surfaces 109, 110 of the nanowire-like channelregions 108) is different than the dielectric constant of the gatedielectric layer 105 extending along the side surfaces 111, 112 of thenanowire-like channel regions 108. Accordingly, the FET 100 includes oneor more separation regions 113 vertically separating adjacentnanowire-like channel regions 108 that are formed of a dielectricmaterial that may be the same as or different than the dielectricmaterial of the gate dielectric layer 105 of the gate stack 104.Providing one or more dielectric layers extending along the upper andlower surfaces 109, 110 of the nanowire-like channel regions 105 thathave a different dielectric constant than the gate dielectric layer 105extending along the side surfaces 111, 112 of the nanowire-like channelregions 108 may provide improved electron transport along the upper andlower surfaces 109, 110 of the nanowire-like channel regions 108 and/ormore desired gate coupling to the upper and lower surfaces 109, 110 ofthe nanowire-like channel regions 108.

In one or more embodiments, the nanowire-like channel regions 108 mayhave a channel width W from approximately 3 nm to approximately 8 nm anda channel height H from approximately 4 nm to approximately 12 nm andthe portions of the gate dielectric layer 105 of the gate stack 104extending between the nanowire-like channel regions 108 may have athickness T from approximately 2 nm to approximately 6 nm such thatadjacent nanowire-like channel regions 108 of the fin 103 are separatedby approximately 2 nm to approximately 6 nm. In one or more embodiments,the nanowire-like channel regions 108 may have a channel width W fromapproximately 4 nm to approximately 6 nm and a channel height H fromapproximately 4 nm to approximately 8 nm and the portions of the gatedielectric layer 105 of the gate stack 104 extending between thenanowire-like channel regions 108 may have a thickness T fromapproximately 2 nm to approximately 4 nm such that adjacentnanowire-like channel regions 108 of the fin 103 are separated byapproximately 2 nm to approximately 4 nm. Providing the nanowire-likechannel regions 108 with a channel height H from approximately 4 nm toapproximately 8 nm (e.g., from approximately 3 nm to approximately 7 nm)and providing portions of the gate dielectric layer 105 of the gatestack 104 extending between the nanowire-like channel regions 108, whichmay have with a thickness T from approximately 2 nm to approximately 4nm, may achieve improved electron transport in the nanowire-like channelregions 108 of the fin 103 due to increased injection velocity fromquantum confinement. Additionally, this increased injection velocity isnot substantially offset by increased phonon or surface-roughnessscattering rates. Providing the nanowire-like channel regions 108 with achannel height H from approximately 4 nm to approximately 8 nm (e.g.,from approximately 3 nm to approximately 7 nm) and providing portions ofthe gate dielectric layer 105 of the gate stack 104 extending betweenthe nanowire-like channel regions 108, which may have with a thickness Tfrom approximately 2 nm to approximately 4 nm, may further achieveimproved electrostatic control of the nanowire-like channel regions 108of the fin 103 due to coupling of fringing fields from the gate stack104 to the upper and lower surfaces 109, 110 of the nanowire-likechannel regions 108, thereby reducing short-channel effects and enablingscaling to shorter gate lengths if desired.

In the illustrated embodiment, the FET 100 also includes a second fin103 including a second stack of nanowire-like channel regions 108adjacent to the first fin 103 including the first stack of nanowire-likechannel regions 108. In the illustrated embodiment, the gate stack 104(i.e., the gate dielectric layer 105 and the metal layer 106) extendaround the second fin 103 in the same manner that the gate stack 104extends around the first fin 103. In one or more embodiments, the FET100 may include any other suitable number of fins each including a stackof nanowire-like channel regions 108, such as, for instance, three ormore fins. In one or more embodiments, the first fin 103 (i.e., thefirst stack of nanowire-like channel regions 108) is spaced apart fromthe second fin 103 (i.e., the second stack of nanowire-like channelregions 108) by a distance D at least as great as the separationdistance between adjacent nanowire-like channel regions 108 in the firstand second stacks (e.g., the horizontal separation distance D betweenthe first and second stacks of nanowire-like channel regions 108 is atleast as great as the thickness T of the portions of the gate dielectriclayer 105 vertically separating adjacent nanowire-like channel regions108). In one or more embodiments, the distance D that the first stack ofnanowire-like channel regions 108 is spaced apart from the second stackof nanowire-like channel regions 108 is greater than the separationdistance between adjacent nanowire-like channel regions 108 in the firstand second fins 103.

Additionally, in one or more embodiments, the thickness T of theportions of the gate dielectric layer 105 vertically separating adjacentnanowire-like channel regions 108 is different than a thickness t_(D) ofthe portions of the gate dielectric layer 105 extending along the sidesurfaces 111, 112 of the nanowire-like channel regions 108 (e.g., thethickness T of the portions of the gate dielectric layer 105 extendingalong the upper and lower surfaces 109, 110 of the nanowire-like channelregions 108 is different than the thickness t_(D) of the portions of thegate dielectric layer 105 extending along the side surfaces 111, 112 ofthe nanowire-like channel regions 108). That is, the gate dielectriclayer 105 may have a non-uniform (e.g., varying) thickness. In one ormore embodiments, the thickness T of the portions of the gate dielectriclayer 105 vertically separating adjacent nanowire-like channel regions108 is equal to or less than approximately twice the thickness t_(D) ofthe portions of the gate dielectric layer 105 extending along the sidesurfaces 111, 112 of the nanowire-like channel regions 108.

In one or more embodiments, the thickness t_(D) of the gate dielectriclayer 105 of the gate stack 104 may be from approximately 1 nm toapproximately 3 nm and the thickness t_(M) of the metal layer 106 of thegate stack 104 may be greater than a thickness of a work-function tuningmetal layer having a thickness from approximately 1 nm to approximately5 nm.

In one or more embodiments, the FET 100 may include one or more n-typeFETs and/or one or more p-type FETs. In one or more embodiments, thenanowire-like channel regions 108 may be formed of silicon (Si), theupper and lower surfaces 109, 110 of the nanowire-like channel regions108 have a (100) orientation, and the side surfaces 111, 112 of thenanowire-like channel regions 108 have a (110) orientation. In one ormore embodiments, the nanowire-like channel regions 108 may be formed ofSi, the upper and lower surfaces 109, 110 of the nanowire-like channelregions 108 have a (110) orientation, and the side surfaces 111, 112 ofthe nanowire-like channel regions 108 have a (110) orientation. In oneor more embodiments, the FET 100 includes an n-type FET havingnanowire-like channel regions 108 formed of Si, a p-type FET havingnanowire-like channel regions 108 formed of silicon germanium (SiGe),the upper and lower surfaces 109, 110 of the nanowire-like channelregions have a (110) orientation or a (100) orientation, and the sidesurfaces 111, 112 of the nanowire-like channel regions 108 have a (110)orientation. In one or more embodiments in which the FET 100 includesboth n-type FETs and p-type FETs, the orientation of the upper and lowersurfaces 109, 110 of the nanowire-like channel regions 108 of the n-typeFETs may be the same as the orientation of the upper and lower surfaces109, 110 of the nanowire-like channel regions 108 of the p-type FETs. Inone or more embodiments in which the FET 100 includes both n-type FETsand p-type FETs, the nanowire-like channel regions 108 of both then-type FETs and the p-type FETs may be formed of Si, the upper and lowersurfaces 109, 110 of the nanowire-like channel regions 108 of the n-typeFET may have a (100) orientation, and the upper and lower surfaces 109,110 of the nanowire-like channel regions 108 of the p-type FET may havea (110) orientation. In one or more embodiments in which the FET 100includes both n-type FETs and p-type FETs, the nanowire-like channelregions 108 of both the n-type FETs and the p-type FETs may be formed ofGe, the upper and lower surfaces 109, 110 of the nanowire-like channelregions 108 of the n-type FET may have a (111) orientation, and theupper and lower surfaces 109, 110 of the nanowire-like channel regions108 of the p-type FET may have a (110) orientation. In one or moreembodiments in which the FET 100 includes both n-type FETs and p-typeFETs, the nanowire-like channel regions 108 of the n-type FETs may bemade from Si, Ge, SiGe, or a group III-V material, the nanowire-typechannel regions 108 of the p-type FETs may be made of Si, Ge, or SiGe,and the surface orientation of upper and lower surfaces 109, 110 of thenanowire-like channels 108 of the n-type or p-type FETs may be Si (110),Ge (110) n-type Si FET (100), p-type Si FET (110), n-type Ge FET (111),or p-type Ge FET (110).

In one or more embodiments, the gate dielectric layer 105 of the gatestack 104 may be formed of a high-K dielectric material, such as, forexample, a material having a K greater than 10 (e.g., HFO₂). In one ormore embodiments, the nanowire-like channel regions 108 may be formed ofSi, SiGe, Ge, or a group III-V material, such as indium gallium arsenide(InGaAs), indium arsenide (InAs), or indium antimonide (InSb).

In one or more embodiments, the metal layer 106 of the gate stack 104may include a work-function tuning metal layer. In one or moreembodiments, the metal layer 106 of the gate stack 104 may include alow-resistance metal cladding layer adjacent to the work-function tuningmetal layer.

FIGS. 2A-2K depict tasks of a method of forming a field effecttransistor (FET) according to one embodiment of the present disclosure.As illustrated in FIGS. 2A-2B, the method includes a task oflayer-by-layer deposition of a stack of alternating sacrificial layers201 and conducting channel layers 202 on a silicon substrate 203 suchthat the lowermost sacrificial layer 201 is directly on the siliconsubstrate 203 and each conducting channel layer 202 is between a pair ofsacrificial layers 201. The silicon substrate 203 may include a (100) or(110) silicon (Si) substrate. Although in the illustrated embodiment thetask includes depositing three conducting channel layers 202 and foursacrificial layers 201, in one or more embodiments, the task may includedepositing any other suitable number of conducting channel layers 202and sacrificial layers 201 depending on the desired size of the FET(e.g., the task may include depositing one or more conducting channellayers 202). In one or more embodiments, the sacrificial layers 201 areformed of SiGe and the conducting channel layers 202 are formed of Si.In one or more embodiments, the SiGe material of the sacrificial layers201 may include Ge in the range from approximately 10% to approximately50% (e.g., from approximately 15% to approximately 35% or fromapproximately 20% to approximately 30%). In one or more embodiments, thesacrificial layers 201 have a thickness from approximately 2 nm toapproximately 6 nm (e.g., approximately 2 nm to approximately 4 nm) andthe conducting channel layers 202 have a thickness from approximately 4nm to approximately 12 nm (e.g., a thickness from approximately 4 nm toapproximately 8 nm). In one or more embodiments, the conducting channellayers 202 and the sacrificial layers 201 may not be formed of Si andSiGe, respectively. In one or more embodiments, the conducting channellayers 202 and the sacrificial layers 201 may be any other suitablematerials whereby the sacrificial layers 201 can be selectively etchedrelative to conducting channel layers 202 for n-type FETs, p-type FETs,or both n-type and p-type FETs. In one or more embodiments in which theFET is an n-type FET, the materials of the conducting channel layers 202and the sacrificial layers 201 may be Group III-V materials, such asInGaAs and InP, respectively. In one or more embodiments, the materialsof the conducting channel layers 202 and the sacrificial layers 201 maybe Group IV materials, such as Ge and SiGe, respectively, for eithern-type FETs or p-type FETs. In one or more embodiments in which the FETis a p-type FET, the materials of the conducting channel layers 202 andthe sacrificial layers 201 may be Group IV materials, such as SiGe andSi, respectively.

In one or more embodiments, the conducting channel layers 202 may beformed of Si, upper and lower surfaces of the conducting channel layers202 have a (100) orientation, and sidewalls of the conducting channellayers 202 have a (110) orientation. In one or more embodiments, theconducting channel layers 202 may be formed of Si, the upper and lowersurfaces of the conducting channel layers 202 have a (110) orientation,and the sidewalls of the conducting channel layers 202 have a (110)orientation. In one or more embodiments in which the FET includes bothn-type and p-type FETs, the n-type FET has conducting channel layers 202formed of Si, the p-type FET has conducting channel layers 202 formed ofSiGe, the upper and lower surfaces of the conducting channel layers 202have a (110) orientation or a (100) orientation, and the sidewalls ofthe conducting channel layers 202 have a (110) orientation. In one ormore embodiments in which the FET includes both n-type FETs and p-typeFETs, the orientation of the upper and lower surfaces of the conductingchannel layers 202 of the n-type FETs may be the same as the orientationof the upper and lower surfaces of the conducting channel layers 202 ofthe p-type FETs. In one or more embodiments in which the FET includesboth n-type FETs and p-type FETs, the conducting channel layers 202 ofboth the n-type FETs and the p-type FETs may be formed of Si, the upperand lower surfaces of the conducting channel layers 202 of the n-typeFET may have a (100) orientation, and the upper and lower surfaces ofthe conducting channel layers 202 of the p-type FET may have a (110)orientation. In one or more embodiments in which the FET includes bothn-type FETs and p-type FETs, the conducting channel layers 202 of boththe n-type FETs and the p-type FETs may be formed of Ge, the upper andlower surfaces of the conducting channel layers 202 of the n-type FETmay have a (111) orientation, and the upper and lower surfaces of theconducting channel layers 202 of the p-type FET may have a (110)orientation. In one or more embodiments in which the FET includes bothn-type FETs and p-type FETs, the conducting channel layers 202 of then-type FETs may be made from Si, Ge, SiGe, or a group III-V material,the conducting channel layers 202 of the p-type FETs may be made of Si,Ge, or SiGe, and the surface orientation of upper and lower surfaces ofthe conducting channel layers 202 of the n-type or p-type FETs may be Si(110), Ge (110) n-type Si FET (100), p-type Si FET (110), n-type Ge FET(111), or p-type Ge FET (110).

In one or more embodiments in which the conducting channel layers 202are formed of materials from different groups (e.g., Group IV, GroupIII-V) and/or in which the conducting channel layers 202 do not have thesame surface orientation, the conducting channel layers 202 may beformed by epitaxial growth from a starting material on an insulatorand/or a separate epitaxial growth from a bulk substrate.

With reference now to FIGS. 2C-2D, the method according to oneembodiment of the present disclosure includes a task of patterning andetching the stack of conducting channel layers 202 and sacrificiallayers 201 to form at least one fin 204. The task of patterning andetching the stack of alternating conducting channel layers 202 and thesacrificial layers 201 may be performed by any suitable process ortechnique, such as, for instance, lithography, sidewall-image transfer,or dry etching. In the illustrated embodiment, the task includes formingtwo adjacent fins 204, although in one or more embodiments, the task mayinclude forming any other desired number of fins 204, such as one fin orthree or more fins. As illustrated in FIG. 2C, each of the fins 204includes a stack of nanowire-like channel regions 205 formed from thematerial of the conducting channel layers 202. The task of patterningand etching the stack includes forming the one or more fins with thedesired channel height H, the desired channel width W and, in the caseof two or more fins, forming the fins 204 with the desired horizontalseparation distance D between adjacent fins 204. In one or moreembodiments, the method includes forming two or more fins 204 in whichthe horizontal separation distance D between two adjacent fins 204 is atleast as great as the thickness T of the sacrificial layers 201. In oneor more embodiments, the task may include forming the one or more fins204 with a channel width W from approximately 3 nm to approximately 8nm, such as, for example, a channel width W from approximately 4 nm toapproximately 6 nm. The channel width W of the one or more fins 204 mayvary depending on the type of device into which the FET is designed tobe incorporated. In one or more embodiments, the task of forming the oneor more fins 204 may include a single mask task and a single etch taskor two or more mask and etch tasks. Additionally, in one or moreembodiments, the task may include an etch (e.g., a dry etch) that is notselective to either the channel layer material or the sacrificial layermaterial. Furthermore, the task may be utilized to form one or more fins204 for nFETs and pFETs.

With continued reference to FIG. 2D, the method also includes a task offorming a dummy gate 206 (e.g., a dummy gate formed ofoxide/poly-Si/nitride) and forming an external sidewall spacer 207 byany process known in the art, such as nitride deposition.

The method also includes a task of masking source and drain regions andetching the one or more fins 204 in regions not protected by the dummygate 206 and the external sidewall spacer 207 formed during the taskdescribed above with reference to FIGS. 2C-2D. In one or moreembodiments, the etching of the one or more fins 204 proceeds all theway down to, or into, the silicon substrate 203.

With reference now to FIG. 2E, the method also includes a task offorming source and drain regions 208, 209 (e.g., nFET source and drainregions or pFET source and drains) by, for example, epitaxialdeposition. In one or more embodiments, the source and drain regions208, 209 may be nFET source and drain regions formed from any suitablematerial, such as Si, SiP, or SiCP. In one or more embodiments, the nFETsource and drain regions 208, 209 may be formed of Si having impurities,such as phosphorous (P) or carbon (C). During the task of epitaxialdeposition, the source and drain regions 208, 209 will form from abottom and along sidewalls of the etched region, thereby connecting thesource and drain regions 208, 209 to the nanowire-like channel regions205 and the sacrificial layers 201. Additionally, in one or moreembodiments, during the task of epitaxial deposition, the nFET sourceand drain regions 208, 209 grow from the silicon substrate 203 to enablestrain in the channel regions.

The method also includes a task of removing the masking of the sourceand drain regions 208, 209 (i.e., unmasking the source and drain regions208, 209).

In one or more embodiments, the task of forming the source and drainregions 208, 209 may include a task of forming pFET source and drainregions by, for example, epitaxial deposition. In one or moreembodiments, the task of forming the pFET source and drain regions 208,209 includes depositing a buffer layer of Si having a thickness, forexample, from approximately 1 nm to approximately 5 nm (e.g.,approximately 1.5 nm), followed by depositing a layer of SiGe, SiGeB, ora similar material. In one or more embodiments, the task may includedepositing a SiGe layer having impurities, such as boron (B) or tin(Sn). In one or more embodiments, a portion of the buffer layer adjacentto the sacrificial layers 201 may be formed from SiGe. In one or moreembodiments, a portion of the SiGe of the pFET source and drain regions208, 209 adjacent to the SiGe sacrificial layers 201 may have the sameor different concentration of Ge as the SiGe sacrificial layers 201. Inone or more embodiments in which the sacrificial layers 201 are formedof Si, the task of forming the pFET source and drain regions 208, 209may not include depositing the buffer layer of Si, although in one ormore embodiments, the task of forming the pFET source and drain regions208, 209 may include depositing the buffer layer of Si even when thesacrificial layers 201 are formed of Si. During the task of epitaxialdeposition, the pFET source and drain regions 208, 209 will form from abottom and along sidewalls of the etched region, thereby connecting thesource and drain regions 208, 209 to the nanowire-like channel regions205 and the sacrificial layers 201. Additionally, in one or moreembodiments, during the task of epitaxial deposition, the pFET sourceand drain regions 208, 209 grow from the silicon substrate 203 to enablestrain in the channel regions.

With reference now to FIGS. 2F-2G, the method also includes tasks ofdepositing an interlayer dielectric (ILD) 210, performing chemicalmechanical planarization (CMP) to a top of the dummy gate 206, and thenremoving the dummy gate 206 to expose the one or more fins 204. Withcontinued reference to FIGS. 2F-2G, the method also includes a task ofremoving the SiGe sacrificial layers 201 by wet or dry etch that isselective with respect to Si, including selective with respect to the Sinanowire-like channel regions 205. The selective etching of thesacrificial layers 201 will not etch into the pFET or nFET source anddrain regions 208, 209 because these regions include an Si materialadjacent to the sacrificial layers 201. In one or more embodiments inwhich the sacrificial layers 201 have sufficient dielectric properties(e.g., for nFET, the sacrificial layers 201 are formed of SiGe or InP),the method may not include the task of removing the sacrificial layers201 before a subsequent task, described below, of forming a gate stack211. In one or more embodiments, the method may include partiallyremoving the sacrificial layers 201 prior to the task of forming thegate stack 211.

With reference now to FIGS. 2H-2K, the method also includes forming thegate stack 211 by forming a gate dielectric layer 212 (see FIGS. 2H-2I)and then forming a metal layer 213 (FIGS. 2J-2K) on the gate dielectriclayer 212 by any process or processes known in the art, such asatomic-layer deposition (ALD). During the task of forming the gate stack211, the gate dielectric layer 212, or a portion of the gate dielectriclayer 212, fills the regions of the removed sacrificial layers 201(i.e., the gate dielectric layer 212, or a portion of the gatedielectric layer 212, fills the regions previously occupied by thesacrificial layers 201). The gate dielectric layer 212 also forms overeach of the one or more fins 204 (i.e., the gate dielectric layer 212forms along the sides of the nanowire-like channel regions 205 and alongan upper surface of the uppermost nanowire-like channel region 205 ineach fin 204). Accordingly, following the task of forming the gate stack211, each of the fins 204 includes a stack of two or more nanowire-likechannel regions 205 separated by portions of the gate dielectric layer212. Additionally, during the task of forming the gate stack 211, themetal layer 213 forms on the gate dielectric layer 212 and around eachof the one or more fins 204 such that the metal layer 213 extends alongthe sidewalls of the nanowire-like channel regions 205 and along theupper surface of the uppermost nanowire-like channel region 205 of eachfin 204. Since the gate dielectric layer 212, or a portion of the gatedielectric layer 212, fills the regions of the removed sacrificiallayers 201, the metal layer 213 of the gate stack 211 does not depositinto the regions of the removed sacrificial layers 201. Accordingly,following the task of forming the gate stack 211, the metal layer 213 ofthe gate stack 211 does not extend between the nanowire-like channelregions 205 (i.e., unlike the gate dielectric layer 212, the metal layer213 does not extend along the upper and lower surfaces of each of thenanowire-like channel regions 205).

In one or more embodiments, the method may include a task of forming(e.g., depositing) a dielectric layer in the regions of the removedsacrificial layers 201 and removing (e.g., etching) portions of thedielectric layer along the sidewalls of the nanowire-like channelregions 205 before the task of forming the gate stack 211 (e.g., themethod may include forming a dielectric layer along the upper and lowersurfaces of the nanowire-like channel regions 205 before forming thegate stack 211). The dielectric material of the dielectric layer isdifferent than the dielectric material of the gate dielectric layer 212of the gate stack 211 (e.g., the dielectric layer has a dielectricconstant different than the dielectric constant of the gate dielectriclayer 212). Accordingly, following the task of forming the gate stack211, the dielectric constant of the dielectric layer extending betweenadjacent nanowire-like channel regions 205 (e.g., along upper and lowersurfaces of the nanowire-like regions 205) is different than thedielectric constant of the gate dielectric layer extending along thesidewalls of the nanowire-like channel regions 205. Providing dielectriclayers with different dielectric constants along the upper and lowersurfaces of the nanowire-like channel regions 205 compared to along thesidewalls of the nanowire-like channel regions 205 may provide improvedelectron transport along the upper and lower surfaces of thenanowire-like channel regions 205 and/or more desired gate coupling tothe upper and lower surfaces of the nanowire-like channel regions 205.

The method also includes completing formation of the FET and a circuitincluding one or more of the FETs by tasks known in the art, includingCMP tasks to enable gate metal only in the removed dummy gate regions,followed by a task of contact formation, and a task of back-end-of-line(BEOL) formation. Additionally, in one or more embodiments, the methodmay include forming partial gate-all-around (GAA) FETS, conventionalfull GAA FETs, and/or conventional finFETs on the same chip/circuit asthe FET formed according to the tasks of the present disclosuredescribed above.

With reference now to FIGS. 3A-3B, a CMOS circuit 300 according to oneembodiment of the present disclosure includes an nFET 301 and a pFET302. The nFET 301 includes a source electrode 303, a drain electrode304, and a fin 305 extending between the source and drain electrodes303, 304. In one or more embodiments, the source and drain electrodes303, 304 of the nFET 301 include Si, SiP, or SiCP. The pFET 302 includesa source electrode 306, a drain electrode 307, and a fin 308 extendingbetween the source and drain electrodes 306, 307. In one or moreembodiments, the source and drain electrodes 306, 307 of the pFET 302include an Si buffer layer and a layer of SiGe or SiGeB on the Si bufferlayer. In one or more embodiments, the Si buffer layer may have athickness from approximately 1 nm to approximately 5 nm. The CMOScircuit 300 also includes a gate stack 309 including a gate dielectriclayer 310 and a metal layer 311 on the gate dielectric layer 310. Thesource electrodes 303, 306, the drain electrodes 304, 307, the fins 305,308, and the gate stack 309 are formed on a substrate 312 (e.g., abulk-silicon substrate or a silicon-on-insulator (SOI) substrate). Asillustrated in FIG. 3B, the fin 305 of the nFET 301 and the fin 308 ofthe pFET 302 are each divided or separated into a stack of discretenanowire-like channel regions 313, 314, respectively. Although in theillustrated embodiment the stacks each include three nanowire-likechannel regions 313, 314, in one or more embodiments, the stacks mayeach include any other suitable number of nanowire-like channel regions313, 314, such as two channel regions or more than three channelregions. In one or more embodiments, the nanowire-like channel regions313, 314 may be strained.

As illustrated in FIG. 3B, the gate dielectric layer 310, or a portionof the gate dielectric layer 310, of the gate stack 309 extendscompletely around each of the nanowire-like channel regions 313, 314(i.e., the gate dielectric layer 310, or a portion of the gatedielectric layer 310, of the gate stack 309 extends along an uppersurface 315, 316, a lower surface 317, 318, and a pair of opposingsidewalls or side surfaces 319, 320, 321, 322, respectively, of each ofthe nanowire-like channel regions 313, 314). Accordingly, in theillustrated embodiment, for each pair of adjacent nanowire-like channelregions 313, 314, the gate dielectric layer 310 or a portion of the gatedielectric layer 310 of the gate stack 309 separates the upper surface315, 316 of the underlying nanowire-like channel region 313, 314 fromthe lower surface 317, 318 of the overlying nanowire-like channel region313, 314. Additionally, in the illustrated embodiment, the metal layer311 of the gate stack 309 extends along the side surfaces 319, 320, 321,322 of the nanowire-like channel regions 313, 314 and along the uppersurface 315, 316 of the uppermost nanowire-like channel region 313, 314(i.e., the metal layer 311 extends around or covers the nanowire-likechannel regions 313, 314 of the fins 305, 308) but the metal layer 311does not extend between adjacent nanowire-like channel regions 313, 314or between the lowermost nanowire-like channel region 313, 314 and thesubstrate 312. Accordingly, in the illustrated embodiment, the full gatestack 309 (i.e., the gate dielectric layer 310 and the metal layer 311)does not extend fully or completely around each of the nanowire-likechannel regions 313, 314 such that the nFET 301 and the pFET 302 of thepresent disclosure are a partial gate-all-around (GAA) nFET and apartial GAA pFET, respectively, rather than full GAA FETs. Providing thefull gate stack 309 along the side surfaces 319, 320, 321, 322 of thenanowire-like channels 313, 314 affords improved control of the channelpotential compared to a conventional finFET structure due to gatecoupling to each nanowire-like channel region 313, 314 through the gatedielectric layer 309 along the upper and lower surfaces 315, 316, 317,318 of each nanowire-like channel region 313, 314 in addition to thegate coupling to each nanowire-like channel region 313, 314 through thegate dielectric layer 310 along the side surfaces 319, 320, 321, 322 ofeach of the nanowire-like channel regions 313, 314.

In one or more embodiments, the gate dielectric layer 310 of the gatestack 309 may not extend, or may not substantially extend, betweenadjacent nanowire-like channel regions 313, 314 and the CMOS circuit 300may include a separate dielectric layer vertically separating adjacentnanowire-like channel regions 313, 314. The separate dielectric layermay be formed from a dielectric material different than a dielectricmaterial of the gate dielectric layer 310 of the gate stack 309. Thatis, the dielectric layer may extend along the upper and lower surfaces315, 316, 317, 318 of the nanowire-like channel regions 313, 314 and thegate dielectric layer 310 may extend along the side surfaces 319, 320,321, 322 of the nanowire-like channel regions 313, 314 such that thedielectric constant of the dielectric layer extending between adjacentnanowire-like channel regions 313, 314 (e.g., along upper and lowersurfaces 315, 316, 317, 318 of the nanowire-like channel regions 313,314) is different than the dielectric constant of the gate dielectriclayer 310 extending along the side surfaces 319, 320, 321, 322 of thenanowire-like channel regions 313, 314. Accordingly, the nFET 301 andthe pFET 302 each include one or more separation regions 323, 324,respectively, vertically separating adjacent nanowire-like channelregions 313, 314, respectively, that are formed of a dielectric materialthat may be the same as or different than the dielectric material of thegate dielectric layer 310 of the gate stack 309. Providing one or moredielectric layers extending along the upper and lower surfaces 315, 316,317, 318 of the nanowire-like channel regions 313, 314 that have adifferent dielectric constant than the gate dielectric layer 310extending along the side surfaces 319, 320, 321, 322 of thenanowire-like channel regions 313, 314 may provide improved electrontransport along the upper and lower surfaces 315, 316, 317, 318 of thenanowire-like channel regions 313, 314 and/or more desired gate couplingto the upper and lower surfaces 315, 316, 317, 318 of the nanowire-likechannel regions 313, 314.

In the illustrated embodiment, a channel height H_(nFET) of thenanowire-like channel regions 313 in the nFET 301 is different than achannel height H_(pFET) of the nanowire-like channel regions 314 in thepFET 302. In one or more embodiments, the channel height H_(nFET) of thenanowire-like channel regions 313 in the nFET 301 is less than thechannel height H_(pFET) of the nanowire-like channel regions 314 in thepFET 302. Additionally, in the illustrated embodiment, the nFET 301 hasa vertical separation distance V_(nFET) between adjacent nanowire-likechannel regions 313, and the pFET 302 has a vertical separation distanceV_(pFET) between adjacent nanowire-like channel regions 314. Thevertical separation distance V_(nFET) corresponds to the thickness ofthe separation regions 323 (e.g., the thickness of the gate dielectriclayer 310 between adjacent nanowire-like channel regions 313) and thevertical separation distance V_(pFET) corresponds to the thickness ofthe separation regions 324 (e.g., the thickness of the gate dielectriclayer 310 between adjacent nanowire-like channel regions 314).

In one or more embodiments, the channel height H_(pFET) of thenanowire-like channel regions 314 in the pFET 302 is approximately 5 nm,the channel height H_(nFET) of the nanowire-like channel regions 313 inthe nFET 301 is approximately 3 nm, the vertical separation distanceV_(pFET) between the nanowire-like channel regions 314 in the pFET 302is approximately 3 nm, and the vertical separation distance V_(nFET)between the nanowire-like channel regions 313 in the nFET 301 isapproximately 5 nm. In one or more embodiments, the channel heightH_(pFET) of the nanowire-like channel regions 314 in the pFET 302 isequal to or greater than approximately 4 nm, the channel height H_(nFET)of the nanowire-like channel regions 313 in the nFET 301 is equal to orless than approximately 4 nm, the vertical separation distance V_(pFET)between the nanowire-like channel regions 314 in the pFET 302 is equalto or less than approximately 4 nm, and the vertical separation distanceV_(nFET) between the nanowire-like channel regions 313 in the nFET 301is equal to or greater than approximately 4 nm. In one or moreembodiments, the channel height H_(pFET) of the nanowire-like channelregions 314 in the pFET 302 is equal to or greater than approximately 5nm, the channel height H_(nFET) of the nanowire-like channel regions 313in the nFET 301 is equal to or less than approximately 5 nm, thevertical separation distance V_(pFET) between the nanowire-like channelregions 314 in the pFET 302 is equal to or less than approximately 3 nm,and the vertical separation distance V_(nFET) between the nanowire-likechannel regions 313 in the nFET 301 is equal to or greater thanapproximately 3 nm. In one or more embodiments, the channel heightH_(pFET) of the nanowire-like channel regions 314 in the pFET 302 isapproximately 5 nm, the channel height H_(nFET) of the nanowire-likechannel regions 313 in the nFET 301 is approximately 4 nm, the verticalseparation distance V_(pFET) between the nanowire-like channel regions314 in the pFET 302 is approximately 3 nm, and the vertical separationdistance V_(nFET) between the nanowire-like channel regions 313 in thenFET 301 is approximately 4 nm.

In one or more embodiments, a sum of the channel height H_(pFET) and thevertical separation distance V_(pFET) of the pFET 302 and the sum of thechannel height H_(nFET) and the vertical separation distance V_(nFET) ofthe nFET 301 are each approximately 8 nm. In one or more embodiments, asum of the channel height H_(pFET) and the vertical separation distanceV_(pFET) of the pFET 302 and the sum of the channel height H_(nFET) andthe vertical separation distance V_(nFET) of the nFET 301 are eachapproximately 9 nm. In one or more embodiments, a sum of the channelheight H_(pFET) and the vertical separation distance V_(pFET) of thepFET 302 and the sum of the channel height H_(nFET) and the verticalseparation distance V_(nFET) of the nFET 301 are each from approximately5 nm to approximately 12 nm.

In one or more embodiments, the channel height H_(pFET) of thenanowire-like channel regions 314 in the pFET 302 is approximately 5 nm,the channel height H_(nFET) of the nanowire-like channel regions 313 inthe nFET 301 is approximately 3 nm, the vertical separation distanceV_(pFET) between the nanowire-like channel regions 314 in the pFET 302is approximately 4 nm, and the vertical separation distance V_(nFET)between the nanowire-like channel regions 313 in the nFET 301 isapproximately 6 nm. In one or more embodiments, the channel heightsH_(nFET), H_(pFET) of the nanowire-like channel regions 313, 314 areeach approximately 5 nm, and the vertical separation distances V_(nFET),V_(pFET) are each approximately 4 nm. In one or more embodiments, thechannel height H_(pFET) of the nanowire-like channel regions 314 in thepFET 302 is equal to or greater than approximately 4 nm, the channelheight H_(nFET) of the nanowire-like channel regions 313 in the nFET 301is equal to or less than approximately 4 nm, the vertical separationdistance V_(pFET) between the nanowire-like channel regions 314 in thepFET 302 is equal to or less than approximately 5 nm, and the verticalseparation distance V_(nFET) between the nanowire-like channel regions313 in the nFET is equal to or greater than approximately 5 nm. In oneor more embodiments, the channel height H_(pFET) of the nanowire-likechannel regions 314 in the nFET 302 is equal to or greater thanapproximately 5 nm, the channel height H_(nFET) of the nanowire-likechannel regions 313 in the nFET 302 is equal to or less thanapproximately 5 nm, the vertical separation distance V_(pFET) betweenthe nanowire-like channel regions 314 in the pFET 302 is equal to orless than approximately 4 nm, and the vertical separation distanceV_(nFET) between the nanowire-like channel regions 313 in the nFET 301is equal to or greater than approximately 4 nm.

In one or more embodiments, the nanowire-like channel regions 313, 314of the nFET 301 and the pFET 302 may each have a channel width W fromapproximately 3 nm to approximately 8 nm.

In one or more embodiments, the metal layer 311 of the gate stack 309may include a work-function tuning metal layer. In one or moreembodiments, the metal layer 311 of the gate stack 309 may include alow-resistance metal cladding layer adjacent to the work-function tuningmetal layer. In one or more embodiments, a material of the metal layer311 of the gate stack 309 at the nFET 301 may be different than amaterial of the metal layer 311 of the gate stack 309 at the pFET 302.In one or more embodiments, a thickness t_(D) of the gate dielectriclayer 310 of the gate stack 309 may be from approximately 1 nm toapproximately 3 nm and the thickness t_(M) of the metal layer 311 of thegate stack 309 may be greater than a thickness of a work-function tuningmetal layer having a thickness from approximately 1 nm to approximately5 nm.

In one or more embodiments, the nanowire-like channel regions 313, 314may be formed of silicon (Si), the upper and lower surfaces 315, 316,317, 318 of the nanowire-like channel regions 313, 314 have a (100)orientation, and the side surfaces 319, 320, 321, 322 of thenanowire-like channel regions 313, 314 have a (110) orientation. In oneor more embodiments, the nanowire-like channel regions 313, 314 may beformed of Si, the upper and lower surfaces 315, 316, 317, 318 of thenanowire-like channel regions 313, 314 have a (110) orientation, and theside surfaces 319, 320, 321, 322 of the nanowire-like channel regions313, 314 have a (110) orientation.

FIGS. 4A-4L depict tasks of a method of forming a CMOS circuit includingan nFET and a pFET according to one embodiment of the presentdisclosure. As illustrated in FIGS. 4A-4B, the method includes a task oflayer-by-layer deposition of a stack of alternating sacrificial layers401 and conducting channel layers 402 on a silicon substrate 403 suchthat the lowermost sacrificial layer 401 is directly on the siliconsubstrate 403 and each conducting channel layer 402 is between a pair ofsacrificial layers 401. The silicon substrate 403 may include a (100) or(110) silicon (Si) substrate. Although in the illustrated embodiment,the task includes depositing three conducting channel layers 402 andfour sacrificial layers 401, in one or more embodiments, the task mayinclude depositing any other suitable number of conducting channellayers 402 and sacrificial layers 401 depending on the desired size ofthe nFET and the pFET. In one or more embodiments, the sacrificiallayers 401 are formed of SiGe and the conducting channel layers 402 areformed of Si. In one or more embodiments, the SiGe material of thesacrificial layers 401 may include Ge in the range from approximately10% to approximately 50% (e.g., from approximately 15% to approximately35% or from approximately 20% to approximately 30%). In one or moreembodiments, the sacrificial layers 401 have a thickness fromapproximately 2 nm to approximately 6 nm (e.g., approximately 2 nm toapproximately 4 nm) and the conducting channel layers 402 have athickness from approximately 2 nm to approximately 12 nm (e.g., athickness from approximately 4 nm to approximately 8 nm).

In one or more embodiments, the conducting channel layers 402 and thesacrificial layers 401 may not be formed of Si and SiGe, respectively,but can be any other suitable materials whereby the sacrificial materialcan be etched selective to the conducting channel material. In one ormore embodiments, the materials of the conducting channel layers 402 andthe sacrificial layers 401 may be Group III-V materials, such as InGaAsand InP, respectively. In one or more embodiments, the materials of theconducting channel layers 402 and the sacrificial layers 401 may beGroup IV materials, such as Ge and SiGe, respectively. In one or moreembodiments, the materials of the conducting channel layers 402 and thesacrificial layers 401 may be Group IV materials, such as SiGe and Si,respectively.

In one or more embodiments, the conducting channel layers 402 may beformed of silicon (Si), upper and lower surfaces of the conductingchannel layers 402 have a (100) orientation, and vertical side surfacesof the conducting channel layers 402 have a (110) orientation. In one ormore embodiments, the conducting channel layers 402 may be formed of Si,the upper and lower surfaces of the conducting channel layers 402 have a(110) orientation, and the vertical side surfaces of the conductingchannel layers 402 have a (110) orientation.

With reference now to FIGS. 4C-4D, the method according to oneembodiment of the present disclosure includes a task of patterning andetching the stack of conducting channel layers 402 and sacrificiallayers 401 to form a first fin 404 of the nFET and a second fin 405 ofthe pFET. The task of patterning and etching the stack of alternatingconducting channel layers 402 and the sacrificial layers 401 may beperformed by any suitable process or technique, such as, for instance,lithography, sidewall-image transfer, or dry etching. As illustrated inFIG. 4C, each of the fins 404, 405 includes a stack of nanowire-likechannel regions 406, 407, respectively, formed from the material of theconducting channel layers 402. The task of patterning and etching thestack includes forming the fins 404, 405 with the desired channel widthW and the desired horizontal separation distance D between the fins 404,405. In one or more embodiments, the method includes forming the fins404, 405 such that the horizontal separation distance D between the fins404, 405 is at least as great as the thickness T of the sacrificiallayers 401. In one or more embodiments, the task may include forming thefins 404, 405 with a channel width W from approximately 3 nm toapproximately 8 nm, such as, for example, a channel width W fromapproximately 4 nm to approximately 6 nm. In one or more embodiments,the task of forming the fins 404, 405 may include a single mask task anda single etch task or two or more mask and etch tasks. Additionally, inone or more embodiments, the task may include an etch (e.g., a dry etch)that is not selective to either the channel layer material or thesacrificial layer material.

With continued reference to FIG. 4D, the method also includes a task offorming a dummy gate 408 (e.g., a dummy gate formed ofoxide/poly-Si/nitride) and forming an external sidewall spacer 409 byany process known in the art, such as nitride deposition.

The method also includes a task of masking the second fin 405 of thepFET and etching the first fin 404 of the nFET in regions not protectedby the dummy gate 408 and the external sidewall spacer 409 formed duringthe task described above with reference to FIGS. 4C-4D. In one or moreembodiments, the etching of the first fin 404 of the nFET proceeds allthe way down to, or into, the silicon substrate 403.

With reference now to FIG. 4E, the method also includes a task offorming nFET source and drain regions 410, 411 by, for example,epitaxial deposition. In one or more embodiments, the nFET source anddrain regions 410, 411 may be formed from any suitable material, such asSi, SiP, or SiCP. In one or more embodiments, the nFET source and drainregions 410, 411 may be formed of Si having impurities, such asphosphorous (P) or carbon (C). During the task of epitaxial deposition,the nFET source and drain regions 410, 411 will form from a bottom andalong sidewalls of the etched region, thereby connecting the nFET sourceand drain regions 410, 411 to the nanowire-like channel regions 406 andthe sacrificial layers 401 of the first fin 404. Additionally, in one ormore embodiments, during the task of epitaxial deposition, the nFETsource and drain regions 410, 411 grow from the silicon substrate 403 toenable strain in the channel regions. In one or more embodiments, priorto the forming of the nFET source and drain regions 410, 411, recessregions in the sacrificial layers 401 of the first fin 404 may be formedsuch that the nFET source and drain regions 410, 411 extend furtherinward, such as, for instance, to achieve lower resistance.

The method also includes a task of removing the masking of the secondfin 405 of the pFET (i.e., unmasking the second fin 405) and a task ofmasking the first fin 404 of the nFET.

With continued reference to the embodiment illustrated in FIG. 4E, themethod also includes a task of forming pFET source and drain regions412, 413 by, for example, epitaxial deposition. In one or moreembodiments, the task of forming the pFET source and drain regions 412,413 includes depositing a buffer layer of Si having a thickness, forexample, from approximately 1 nm to approximately 5 nm (e.g.,approximately 1.5 nm), followed by depositing a layer of SiGe, SiGeB, ora similar material. In one or more embodiments, the task may includedepositing a SiGe layer having impurities, such as boron (B) or tin(Sn). In one or more embodiments, a portion of the buffer layer adjacentto the sacrificial layers 401 may be formed from SiGe. In one or moreembodiments, a portion of the SiGe of the pFET source and drain regions412, 413 adjacent to the SiGe sacrificial layers 401 may have the sameor different concentration of Ge as the SiGe sacrificial layers 401. Inone or more embodiments in which the sacrificial layers 401 are formedof Si, the task of forming the pFET source and drain regions 412, 413may not include depositing the buffer layer of Si, although in one ormore embodiments, the task of forming the pFET source and drain regions412, 413 may include depositing the buffer layer of Si even when thesacrificial layers 401 are formed of Si. During the task of epitaxialdeposition, the pFET source and drain regions 412, 413 will form from abottom and along sidewalls of the etched region, thereby connecting thepFET source and drain regions 412, 413 to the nanowire-like channelregions 407 and the sacrificial layers 401. Additionally, in one or moreembodiments, during the task of epitaxial deposition, the pFET sourceand drain regions 412, 413 grow from the silicon substrate 403 to enablestrain in the channel regions. In one or more embodiments, prior to theforming of the pFET source and drain regions 412, 413, recess regions inthe sacrificial layers 401 may be formed such that the pFET source anddrain regions 412, 413 extend further inward, such as, for instance, toachieve lower resistance.

In one or more embodiments, the tasks of forming the pFET source anddrain regions 412, 413 and the nFET source and drain regions 410, 411may be reversed. For instance, in one or more embodiments, the methodmay include tasks of masking the first fin 404 of the nFET, forming thepFET source and drain regions 412, 413, unmasking the first fin 404,masking the second fin 405 of the pFET, and then forming the nFET sourceand drain regions 410, 411.

With reference now to FIGS. 4F-4G, the method also includes tasks ofdepositing an interlayer dielectric (ILD) 414, performing chemicalmechanical planarization (CMP) to a top of the dummy gate 408, and thenremoving the dummy gate 408 to expose the first and second fins 404, 405of the nFET and the pFET, respectively.

With continued reference to FIGS. 4F-4G, the method also includes a taskof removing the SiGe sacrificial layers 401 by wet or dry etch that isselective with respect to Si, including selective with respect to the Sinanowire-like channel regions 406, 407. The selective etching of thesacrificial layers 401 will not etch into the nFET and pFET source anddrain regions 410, 411, 412, 413 because these regions include an Simaterial adjacent to the sacrificial layers 401.

With reference now to FIG. 4H, the method also includes a task ofmasking the second fin 405 of the pFET (e.g., performing a second orsubsequent masking of the second fin 405 of the pFET). The method alsoincludes a task of removing a portion of each of the nanowire-likechannel regions 406 of the first fin 404 (e.g., removing upper and lowerportions of each of the nanowire-like channel regions 406 of the firstfin 404). The task of removing a portion of each of the nanowire-likechannel regions 406 of the first fin 404 may be performed by anysuitable process or processes, such as, for instance, strip, cleaning,ashing, etching, and/or oxidation processes. Following the task ofremoving a portion of each of the nanowire-like channel regions 406 ofthe first fin 404, each of the nanowire-like channel regions 406 of thefirst fin 404 has a height H_(nFET) that is less than a height H_(pFET)of each of the nanowire-like channel regions 407 of the second fin 405.Additionally, in the illustrated embodiment, following the task ofremoving a portion of each of the nanowire-like channel regions 406 ofthe first fin 404, a vertical separation distance V_(nFET) betweenadjacent nanowire-like channel regions 406 in the first fin 404 isgreater than a vertical separation distance V_(pFET) between adjacentnanowire-like channel regions 407 in the second fin 405.

In one or more embodiments, the method may include a task of masking thefirst fin 404 of the nFET (e.g., performing a second or subsequentmasking of the first fin 404 of the pFET), and a task of removing aportion of each of the nanowire-like channel regions 407 of the secondfin 405 (e.g., removing upper and lower portions of each of thenanowire-like channel regions 407 of the second fin 405). In one or moreembodiments, the portion of the nanowire-like channel regions 407 of thesecond fin 405 that is removed (e.g., etched away) is less than theportion of the nanowire-like channel regions 406 of the first fin 404that is removed such that the height H_(nFET) of the nanowire-likechannel regions 406 of the first fin 404 is less than the heightH_(pFET) of each of the nanowire-like channel regions 407 of the secondfin 405.

In one or more embodiments, following the task of removing a portion ofeach of the nanowire-like channel regions 406 of the first fin 404, thechannel height H_(pFET) of the nanowire-like channel regions 407 in thepFET is approximately 5 nm, the channel height H_(nFET) of thenanowire-like channel regions 406 in the nFET is approximately 3 nm, thevertical separation distance V_(pFET) between the nanowire-like channelregions 407 in the pFET is approximately 3 nm, and the verticalseparation distance V_(nFET) between the nanowire-like channel regions406 in the nFET is approximately 5 nm. In one or more embodiments, thechannel height H_(pFET) of the nanowire-like channel regions 407 in thepFET is equal to or greater than approximately 4 nm, the channel heightH_(nFET) of the nanowire-like channel regions 406 in the nFET is equalto or less than approximately 4 nm, the vertical separation distanceV_(pFET) between the nanowire-like channel regions 407 in the pFET isequal to or less than approximately 4 nm, and the vertical separationdistance V_(nFET) between the nanowire-like channel regions 406 in thenFET is equal to or greater than approximately 4 nm. In one or moreembodiments, the channel height H_(pFET) of the nanowire-like channelregions 407 in the pFET is equal to or greater than approximately 5 nm,the channel height H_(nFET) of the nanowire-like channel regions 406 inthe nFET is equal to or less than approximately 5 nm, the verticalseparation distance V_(pFET) between the nanowire-like channel regions407 in the pFET is equal to or less than approximately 3 nm, and thevertical separation distance V_(nFET) between the nanowire-like channelregions 406 in the nFET is equal to or greater than approximately 3 nm.In one or more embodiments, the channel height H_(pFET) of thenanowire-like channel regions 407 in the pFET is approximately 5 nm, thechannel height H_(nFET) of the nanowire-like channel regions 406 in thenFET is approximately 4 nm, the vertical separation distance V_(pFET)between the nanowire-like channel regions 407 in the pFET isapproximately 3 nm, and the vertical separation distance V_(nFET)between the nanowire-like channel regions 406 in the nFET isapproximately 4 nm.

In one or more embodiments, following the task of removing a portion ofeach of the nanowire-like channel regions 406 of the first fin 404, asum of the channel height H_(pFET) and the vertical separation distanceV_(pFET) of the pFET and the sum of the channel height H_(nFET) and thevertical separation distance V_(nFET) of the nFET are each approximately8 nm. In one or more embodiments, a sum of the channel height H_(pFET)and the vertical separation distance V_(pFET) of the pFET and the sum ofthe channel height H_(nFET) and the vertical separation distanceV_(nFET) of the nFET are each approximately 9 nm. In one or moreembodiments, a sum of the channel height H_(pFET) and the verticalseparation distance V_(pFET) of the pFET and the sum of the channelheight H_(nFET) and the vertical separation distance V_(nFET) of thenFET are each from approximately 5 nm to approximately 12 nm.

In one or more embodiments, the channel height H_(pFET) of thenanowire-like channel regions 407 in the pFET is approximately 5 nm, thechannel height H_(nFET) of the nanowire-like channel regions 406 in thenFET is approximately 3 nm, the vertical separation distance V_(pFET)between the nanowire-like channel regions 407 in the pFET isapproximately 4 nm, and the vertical separation distance V_(nFET)between the nanowire-like channel regions 406 in the nFET isapproximately 6 nm. In one or more embodiments, the channel heightsH_(nFET), H_(pFET) of the nanowire-like channel regions 406, 407 areeach approximately 5 nm, and the vertical separation distances V_(nFET),V_(pFET) are each approximately 4 nm. In one or more embodiments, thechannel height H_(pFET) of the nanowire-like channel regions 407 in thepFET is equal to or greater than approximately 4 nm, the channel heightH_(nFET) of the nanowire-like channel regions 406 in the nFET is equalto or less than approximately 4 nm, the vertical separation distanceV_(pFET) between the nanowire-like channel regions 407 in the pFET isequal to or less than approximately 5 nm, and the vertical separationdistance V_(nFET) between the nanowire-like channel regions 406 in thenFET is equal to or greater than approximately 5 nm. In one or moreembodiments, the channel height H_(pFET) of the nanowire-like channelregions 407 in the pFET is equal to or greater than approximately 5 nm,the channel height H_(nFET) of the nanowire-like channel regions 406 inthe nFET is equal to or less than approximately 5 nm, the verticalseparation distance V_(pFET) between the nanowire-like channel regions407 in the pFET is equal to or less than approximately 4 nm, and thevertical separation distance V_(nFET) between the nanowire-like channelregions 406 in the nFET is equal to or greater than approximately 4 nm.

With reference now to FIGS. 4I-4L, the method also includes forming agate stack 415 by forming a gate dielectric layer 416 (see FIGS. 4I-4J)and then forming a metal layer 417 (FIGS. 4K-4L) on the gate dielectriclayer 416 by any process or processes known in the art, such asatomic-layer deposition (ALD). During the task of forming the gate stack415, the gate dielectric layer 416, or a portion of the gate dielectriclayer 416, fills the regions of the removed sacrificial layers 401(i.e., the gate dielectric layer 416, or a portion of the gatedielectric layer 416, fills the regions previously occupied by thesacrificial layers 401). The gate dielectric layer 416 also forms overeach of the first and second fins 404, 405 of the nFET and the pFET,respectively (i.e., the gate dielectric layer 416 forms along the sidesof the nanowire-like channel regions 406, 407 and along an upper surfaceof the uppermost nanowire-like channel region 406, 407 in each of thefirst and second fins 404, 405). Accordingly, following the task offorming the gate stack 415, each of the first and second fins 404, 405includes a stack of two or more nanowire-like channel regions 406, 407,respectively, separated by portions of the gate dielectric layer 416.Additionally, during the task of forming the gate stack 415, the metallayer 417 forms on the gate dielectric layer 416 and around each of thefirst and second fins 404, 405 such that the metal layer 417 extendsalong the sidewalls of the nanowire-like channel regions 406, 407 andalong the upper surface of the uppermost nanowire-like channel region406, 407 of each of the first and second fins 404, 405. Since the gatedielectric layer 416, or a portion of the gate dielectric layer 416,fills the regions of the removed sacrificial layers 401, the metal layer417 of the gate stack 415 does not deposit into the regions of theremoved sacrificial layers 401. Accordingly, following the task offorming the gate stack 415, the metal layer 417 of the gate stack 415does not extend between adjacent nanowire-like channel regions 406, 407in the first fin 404 or the second fin 405, respectively, or between thelowermost nanowire-like channel region 406, 407 and the substrate 403(i.e., unlike the gate dielectric layer 416, the metal layer 417 doesnot extend along the upper and lower surfaces of each of thenanowire-like channel regions 406, 407).

In one or more embodiments, the method may include a task of forming(e.g., depositing) a dielectric layer in the regions of the removedsacrificial layers 401 and removing (e.g., etching) portions of thedielectric layer along the sidewalls of the nanowire-like channelregions 406, 407 before the task of forming the gate stack 415 (e.g.,the method may include forming a dielectric layer along the upper andlower surfaces of the nanowire-like channel regions 406, 407 beforeforming the gate stack 415). The dielectric material of the dielectriclayer is different than the dielectric material of the gate dielectriclayer 416 of the gate stack 415 (e.g., the dielectric layer has adielectric constant different than the dielectric constant of the gatedielectric layer 416). Accordingly, following the task of forming thegate stack 415, the dielectric constant of the dielectric layerextending between adjacent nanowire-like channel regions 406, 407 (e.g.,along upper and lower surfaces of the nanowire-like regions 406, 407) isdifferent than the dielectric constant of the gate dielectric layer 416extending along the sidewalls of the nanowire-like channel regions 406,407. Providing dielectric layers with different dielectric constantsalong the upper and lower surfaces of the nanowire-like channel regions406, 407 compared to along the sidewalls of the nanowire-like channelregions 406, 407 may provide improved electron transport along the upperand lower surfaces of the nanowire-like channel regions 406, 407 and/ormore desired gate coupling to the upper and lower surfaces of thenanowire-like channel regions 406, 407.

The method also includes completing formation of the CMOS circuit bytasks known in the art, including CMP tasks to enable gate metal only inthe removed dummy gate regions, followed by a task of contact formation,and a task of back-end-of-line (BEOL) formation. Additionally, in one ormore embodiments, the method may include forming partial gate-all-around(GAA) FETs, conventional full GAA FETs, and/or conventional finFETs onthe same chip/circuit as the CMOS circuit formed according to the tasksof the present disclosure described above.

In one or more embodiments, the method of the present disclosure may beutilized to forms fins of different channel widths and channel heightsfor different sets of devices by performing different layer depositionsfor the different sets of devices. For instance, layers of Si/SiGematerial may be deposited while the pFET region is masked to achieve thedesired nFET channel height and spacing. Layers of Si/SiGe material maythen be deposited while the nFET region is masked to achieve the desiredpFET channel height and spacing. A common sacrificial layer process andcommon gate dielectric fill of the vertical separation regions may thenbe utilized as desired.

FIG. 5 is a graph depicting the saturated drain current (Idsat) of annFET according to one or more embodiments of the present disclosure as afunction of the channel height H_(nFET) of the nanowire-like channelregions. As illustrated in FIG. 5, the Idsat of a regular voltagethreshold (RVT) nFET having a channel length Lg of approximately 15 nmincreases by approximately 17% if the channel height H_(nFET) of thenanowire-like channel regions is decreased from approximately 40 nm toapproximately 4 nm (i.e., the Idsat increases from approximately 600μA/μm with a channel height H_(nFET) of approximately 40 nm toapproximately 700 μA/μm with a channel height H_(nFET) of approximately4 nm). The Idsat of an RVT nFET having a channel length Lg ofapproximately 10 nm increases by approximately 40% if the channel heightH_(nFET) of the nanowire-like channel regions is decreased fromapproximately 40 nm to approximately 4 nm (i.e., the Idsat increasesfrom approximately 470 μA/μm with a channel height H_(nFET) ofapproximately 40 nm to approximately 650 μA/μm with a channel heightH_(nFET) of approximately 4 nm).

Additionally, as illustrated in FIG. 5, the Idsat of a super low voltagethreshold (SLVT) nFET having a channel length Lg of approximately 15 nmincreases by approximately 10% if the channel height H_(nFET) of thenanowire-like channel regions is decreased from approximately 40 nm toapproximately 4 nm (i.e., the Idsat increases from approximately 910μA/μm with a channel height H_(nFET) of approximately 40 nm toapproximately 1000 μA/μm with a channel height H_(nFET) of approximately4 nm). The Idsat of a SLVT nFET having a channel length Lg ofapproximately 10 nm increases by approximately 25% if the channel heightH_(nFET) of the nanowire-like channel regions is decreased fromapproximately 40 nm to approximately 4 nm (i.e., the Idsat increasesfrom approximately 800 μA/μm with a channel height H_(nFET) ofapproximately 40 nm to approximately 1000 μA/μm with a channel heightH_(nFET) of approximately 4 nm).

FIG. 6 is a graph depicting the saturated drain current (Idsat) of apFET according to one or more embodiments of the present disclosure as afunction of the channel height H_(pFET) of the nanowire-like channelregions. As illustrated in FIG. 6, the Idsat of a pFET having a channellength Lg of approximately 15 nm increases by approximately 11% if thechannel height H_(pFET) of the nanowire-like channel regions isdecreased from approximately 15 nm to approximately 5 nm (i.e., theIdsat increases from approximately 560 μA/μm with a channel heightH_(pFET) of approximately 15 nm to approximately 620 μA/μm with achannel height H_(pFET) of approximately 5 nm). The Idsat of a pFEThaving a channel length Lg of approximately 10 nm increases byapproximately 34% if the channel height H_(pFET) of the nanowire-likechannel regions is decreased from approximately 15 nm to approximately 5nm (i.e., the Idsat increases from approximately 460 μA/μm with achannel height H_(pFET) of approximately 15 nm to approximately 620μA/μm with a channel height H_(pFET) of approximately 5 nm).

What is claimed is:
 1. A CMOS circuit, comprising: a partial GAA nFET;and a partial GAA pFET, wherein the partial GAA nFET and the partial GAApFET each comprise: a fin comprising a stack of nanowire-like channelregions, the stack comprising at least a first nanowire-like channelregion and a second nanowire-like channel region stacked on the firstnanowire-like channel region; a dielectric separation region between thefirst and second nanowire-like channel regions, the dielectricseparation region extending completely from a surface of the secondnanowire-like channel region facing the first nanowire-like channelregion to a surface of the first nanowire-like channel region facing thesecond nanowire-like channel region; a source electrode and a drainelectrode on opposite sides of the fin; and a gate stack extending alonga pair of sidewalls of the stack of nanowire-like channel regions, thegate stack comprising a gate dielectric layer and a metal layer on thegate dielectric layer, wherein the metal layer of the gate stack doesnot extend between the first and second nanowire-like channel regions,and wherein an nFET channel height of each of the first and secondnanowire-like channel regions of the partial GAA nFET is different thana pFET channel height of each of the first and second nanowire-likechannel regions of the partial GAA pFET.
 2. The CMOS circuit of claim 1,wherein the nFET channel height is less than the pFET channel height. 3.The CMOS circuit of claim 2, wherein the nFET channel height is fromapproximately 2 nm to approximately 6 nm, and wherein the pFET channelheight is from approximately 4 nm to approximately 6 nm.
 4. The CMOScircuit of claim 2, wherein the nFET channel height is fromapproximately 3 nm to approximately 4 nm, and wherein the pFET channelheight is from approximately 4 nm to approximately 5 nm.
 5. The CMOScircuit of claim 1, wherein a height of the dielectric separation regionof the partial GAA nFET is different than a height of the dielectricseparation region of the partial GAA pFET.
 6. The CMOS circuit of claim5, wherein the height of the dielectric separation region of the partialGAA nFET is greater than the height of the dielectric separation regionof the pFET.
 7. The CMOS circuit of claim 1, wherein a first sum of thenFET channel height and a height of the dielectric separation region ofthe partial GAA nFET is substantially equal to a second sum of the pFETchannel height and a height of the dielectric separation region of thepartial GAA pFET.
 8. The CMOS circuit of claim 8, wherein the first andsecond sums are each from approximately 5 nm to approximately 12 nm. 9.The CMOS circuit of claim 1, wherein the dielectric separation regionsof the partial GAA nFET and the partial GAA pFET each comprise a portionof the gate dielectric layer of the gate stack.
 10. The CMOS circuit ofclaim 1, wherein a dielectric material of the dielectric separationregion of the partial GAA nFET and the partial GAA pFET is differentthan a dielectric material of the gate dielectric layer of the partialGAA nFET and the partial GAA pFET.
 11. The CMOS circuit of claim 1,wherein the gate dielectric layer has a thickness from approximately 1nm to approximately 3 nm.
 12. The CMOS circuit of claim 1, wherein thefirst and second nanowire-like channel regions of the partial GAA nFETor the partial GAA pFET each have a width from approximately 3 nm toapproximately 8 nm.
 13. A method of forming a CMOS circuit comprising apartial GAA nFET and a partial GAA pFET, the method comprising: forminga stack of alternating sacrificial layers and conducting channel layerson a substrate; etching the stack to form a first fin of the partial GAAnFET and a second fin of the partial GAA pFET, each of the first andsecond fins comprising a stack of nanowire-like channel regions, thestack comprising at least a first nanowire-like channel region and asecond nanowire-like channel region stacked on the first nanowire-likechannel region; forming source and drain electrodes for the partial GAAnFET; forming source and drain electrodes for the partial GAA pFET;masking the second fin of the partial GAA pFET; removing a portion ofthe stack of nanowire-like channel regions of the first fin such that aheight of each of the first and second nanowire-like channel regions ofthe first fin is less than a height of each of the first and secondnanowire-like channel regions of the second fin; forming, for each ofthe first and second fins, a dielectric separation region between thefirst and second nanowire-like channel regions of the stack ofnanowire-like channel regions, the dielectric separation regionextending completely from a surface of the second nanowire-like channelregion facing the first nanowire-like channel region to a surface of thefirst nanowire-like channel region facing the second nanowire-likechannel region; and forming a gate stack comprising a gate dielectriclayer and a metal layer on the gate dielectric layer, wherein the gatestack extends along a pair of sidewalls of the stack of nanowire-likechannel regions for each of the first and second fins, and wherein, foreach of the first and second fins, the metal layer of the gate stackdoes not extend between the first and second nanowire-like channelregions of the stack of nanowire-like channel regions.
 14. The method ofclaim 13, wherein the removing the portion of the stack of nanowire-likechannel regions of the first fin comprises a process or processesselected from the group consisting of a strip process, a cleaningprocess, an ashing process, an etching process, an oxidation process,and combinations thereof.
 15. The method of claim 13, wherein thedielectric separation region of the first fin or the second fin isformed during the forming of the gate stack, and wherein the dielectricseparation region of the first fin or the second fin comprises a portionof the gate dielectric layer of the gate stack.
 16. The method of claim13, wherein the dielectric separation region of each of the first andsecond fins is formed before the forming of the gate stack, and whereina material of the dielectric separation region of each of the first andsecond fins is different than a material of the gate dielectric layer.17. The method of claim 13, wherein the forming the source and drainelectrodes of the partial GAA pFET comprises depositing an Si bufferlayer followed by depositing a layer of SiGe or SiGeB.
 18. The method ofclaim 13, wherein the forming the source and drain electrodes of thepartial GAA nFET comprises depositing an Si layer.
 19. The method ofclaim 13, wherein the conducting channel layers comprise Si, thesacrificial layers comprise SiGe, and wherein Ge content of the SiGe isfrom approximately 10% to approximately 50%.
 20. The method of claim 13,further comprising removing a portion of the stack of nanowire-likechannel regions of the second fin, wherein the removing of the portionof the stack of nanowire-like channel regions of the first fin isgreater than the removing of the portion of the stack of nanowire-likechannel regions of the second fin.